The present invention relates to non-destructive inspection (NDI) instruments, and more particularly to a multiple mode digitization system for said instruments which is well suited to accommodate multiple probe types.
Any discussion of the related art throughout this specification should in no way be considered as an admission that such art is widely known or forms a part of the common general knowledge in the field.
As digital signal processing electronics have grown smaller, more economical, and power efficient over the last several years, NDI instruments employing them have become increasingly more powerful and capable. Signal processing and data analysis once reserved for post inspection processes can now be performed in real time, and in some cases directly on handheld NDI instruments. Ultrasonic phased array systems, for example, can now be realized in small, portable instruments.
This dramatic increase in signal processing power has led to a new generation of NDI instruments. Making use of state of the art digital signal processing technology and techniques, a single compact NDI instrument can be realized which performs multiple inspection functions each of which requiring a separate input time and instrument mode—for example, but not limited to, an instrument which can function with a lower bandwidth array probe as well as a higher bandwidth, high dynamic range single element probe. Despite these advances in digital signal processing technology, however, a new design limitation has been encountered.
NDI probes with multiple sensor elements—that is to say probes which provide a plurality of individual signals to the instrument—such as array probes require multiple analog to digital converters to process all of the signals in parallel. While numerous post processing and multiple pulser and receiver firing methods (combining the results of a number of iterative measurements) can be used to reduce the number of analog to digital converters required in the digitization system of such an NDI instrument, simultaneous sampling of all signals is often required for real time signal analysis—such as that which is becoming increasingly more accessible through the improvement of digital signal processing technology. Despite the increased cost and size of such instruments, there exists an increasing need for systems which provide a dedicated analog to digital converter for each analog signal in a given probe.
Adding a second or third probe input to such an NDI instrument can further increase the number of analog to digital converters required. As the multiple probe inputs will likely have different numbers of sensor elements, bandwidth needs, and sampling rate requirements, simply reusing the existing analog to digital converters becomes problematic. While adding more and more analog to digital converters to the digitization system of an NDI instrument is certainly possible, it can quickly become impractical, as the size, cost, and power requirements of the instrument grow to accommodate the additional circuitry. Although digital signal processing technology has reached a point to allow for a multiple input/multiple mode NDI instrument, without a more efficient digitization system, such an instrument will be overly large, impractical, and not price competitive.
Accordingly, it would be advantageous to provide a digitization system for a NDI instrument which could accommodate multiple inputs without the need for a dedicated set of analog to digital converters on each input. Further, it would be advantageous if this digitization system were well suited for use with multiple input types, such as, but not limited to, array probes, single element probes, and the set of analog signals generated through a high bandwidth, high dynamic range probe receiver circuit such as the one disclosed in US 2007-0084288 by Thomas (incorporated herein by reference). It would also be advantageous if this digitization system were well suited to compensate for signal propagation delays experienced by the analog signals prior to digitization. It would further be advantageous if this digitization system were able to provide different sampling rates for each input without the need for multiple clock frequencies.